Gardeners in California live with the constant specter of drought. Those in other parts of the country are burdened with the challenges of too much rain.
Clay soils, gushing storms and swollen groundwater combine to present wet, challenging sites (not to mention the horror of a wet basement). The problem seems to be worsening.
Such frequent cloudbursts reveal areas of poor drainage, waterlogged soils and even ponding — conditions that can cause cherished plants to decline and die. The flooding makes dense soils even more compacted, further denying roots the oxygen they need. Old white oaks in urban settings have been dying recently, probably as a delayed response to deluges.
The problem can be addressed in several ways, though they may not be easy. One approach is to put in a surface swale or to install buried pipes, but this only moves the water elsewhere, and if you send it off your property, you may be running afoul of laws and regulations.
Another option is to build a rain garden, an area that holds storm water until it can percolate into the soil. It sounds simple, but it requires some serious soil excavation and replacement with a gravelly soil mix and other elements, including plants that can take both periodic flooding and drought conditions. Because this palette is limited and the placement of each plant is critical, the result is often a paucity of plantings around a stone-filled ditch.
The third option is easier. In an area where the plants are dying because of rain, you can take them out and replace them with perennials, ground covers, shrubs and trees that have evolved to take flood-plain conditions. While you are doing this, add loads of organic matter, such as leaf mold, to the soil, which will elevate the beds a little and allow them to hold more moisture. In making these beds, feel free to expand into lawn areas; a lawn in wet, compacted soil will never thrive.
My advice is not to plant just the odd tree or bush, but to consider a comprehensive, multilayered, plant-rich makeover, which will turn a problem location into a landscape asset. Also, the more vegetation you have, the quicker the water will be removed by the plants themselves. The compromise is that during periods of dryness and drought, you will have to keep these moisture lovers watered, especially during their first year or two of establishment.
Maura McMahon, a reader in Arlington, Virginia, recently wrote to me for planting suggestions for such an area after one of her prized, mature redbud trees had died, probably as a result of soil wetness. The redbud bed is between the edge of a patio and the property fence, and the site narrows to roughly 10 feet as it runs past the side of the house.
She wondered about a magnolia or a birch as a replacement, needing a tree that would provide both screening and shade, but would also look good with the remaining redbud.
A couple of flood-tolerant magnolias come to mind, the first being the southern magnolia, with its fantastic white blossoms and big, glossy leaves. One of the smaller varieties might work in her space, such as Little Gem or Teddy Bear, also known as Southern Charm.
The sweetbay magnolia is a smaller, more refined species, with blue-green leaves that may drop in winter, depending on the variety and how cold it gets. It comes as a multi-stemmed big shrub or as a single-trunked tree, so you need to select your preferred type of plant when buying.
Birches are more challenging. The white-barked species struggle in hot, humid climates, and most grow to be quite large.
Another option might be one of the narrower varieties of the bald cypress, such as Prairie Sentinel or Morris.
My preference would be a sweetbay magnolia, or maybe three in a grouping. If I had an expansive wet site where tree size were no object, I would plant a swamp chestnut oak, a sycamore, a blackgum or even one of the improved varieties of red maple. Or better yet, a grove of any of these.
Alongside the house, I would get rid of the turf, put in stone pavers and plant the area along the fence with a row of winterberry holly (Ilex verticillata), which can be shaped to become exquisite little trees, with lower branches removed for path access. You need a male plant in the mix for berry set.
Another native holly, the inkberry, comes in the form of a fine-textured evergreen shrub, grows to about waist height and is perfect as a low hedge or any way you might use a boxwood, which is definitely not a plant for wet sites. The inkberry sets black berries that provide sustenance to birds in the winter. Again, one male plant is needed among the female ones for berry set. Inkberry’s botanic name is Ilex glabra, not to be confused with the Japanese holly, Ilex crenata, which does not like wet soil.
The chokeberry is another useful native plant for a full planting bed in wet areas. It develops as a multi-stemmed shrub with an open habit that grows to about 6 feet, sets pretty berries and has red fall color. The red chokeberry (Aronia arbutifolia) has red berries; look for the improved variety Brilliantissima. The black chokeberry (Aronia melanocarpa) is not as large a shrub, but both species will spread by suckers — if you want them to. They have dome-like clusters of white flowers in April that are pretty but not spectacular.
You could cover the ground of a wetland garden with all manner of herbaceous plants, including sedges, hostas and, especially, ferns. Throw in some hardy begonias, lobelias and Siberian, Japanese or Louisiana irises, and you will welcome the storm clouds.
Gardening tip: Wait for the warmer soils of May to sow directly the seeds of heat-loving annuals and vegetables, like sweet corn, beans, sunflowers, zinnias, okra and cosmos.